Does water boil at a lower temperature at high altitude?

Yes. Water boils at a lower temperature higher up because there is less air pressure pushing down on it. At 5,000 feet (about 1,500 m) it boils at about 95°C (203°F) instead of 100°C, so food cooks more slowly.

What's actually true

Water boils at a lower temperature the higher up you go. Water boils when its vapour pressure matches the air pressure pushing down on it. High up there is less air above you, so water boils at a lower temperature. At 5,000 feet (about 1,500 m) it boils at about 95°C (203°F) instead of 100°C, so pasta and eggs take longer to cook.

Takeaway: In the mountains, boiling water is cooler, so add cooking time.

Why people believe it

This one is true but often misunderstood. People assume boiling means 'as hot as water gets', so a pot that boils sooner in the mountains seems to cook faster. In fact the water stops getting hotter once it boils, and at altitude that ceiling is lower. Pasta, eggs and beans spend the same time in cooler water, which is why recipes for high places add cooking time or use pressure cookers.

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